1. Field of the Invention
The present invention relates to an air conditioning system for vehicles, and, more specifically, to an air conditioning system suitable as an air conditioner for use in a work vehicle.
2. Description of the Related Art
In a vehicle having a radiator supplying water to an engine, the radiator is generally mounted in an engine compartment together with other equipments for an air conditioner. A compressor provided in a cooling circuit of the air conditioner is generally driven by using the power of an engine. If the consumptive power of the engine is too much, the engine may heat up and the water temperature in the radiator may be too hot, thereby causing the vehicle to overheat. If the vehicle overheats or a warning that the vehicle is about to overheat occurs, the operation of the vehicle is stopped or a restriction on the operation of the vehicle occurs.
In work vehicles, for example power shovels, common sized cabins are frequently used regardless of the size or weight of the vehicles. Thus, the specification and abilities of air conditioners required for such common cabins may be substantially the same. However, the engine and equipment around the engine, including the radiator, tend to become smaller as the size and weight of the vehicle decreases. Therefore, in smaller sized work vehicles:
a) The amount of power consumed to drive the compressor of the air conditioner and thus the total consumptive power of the engine is increased, and the engine tends to heat up.
b) The condenser covers a greater amount of area of the radiator so that the ability of the radiator to handle heat radiation decreases.
c) Because generally, the engine compartment is not too wide, the ability to exhaust heat is not good. Therefore, heat tends to be trapped in the engine compartment, and a) and b) may be exasperated. As a result, in smaller vehicles the water temperature in the radiator tends to be high, and overheating often occurs.
Moreover, in a work vehicle, a door and/or a window may frequently be open. This causes the cooling load to increase, which causes the heat radiated from the condenser to increase, which results a decrease in the ability of the radiator to handle the heat radiation. As a result, the water temperature in the radiator may increase and the vehicle may overheat.
Further, in a work vehicle, a door or a window of a cabin, or both, may be opened during vehicle operations. In such situation, the cooling load may increase such that it is difficult to achieve a comfortable degree of air conditioning for the operator. For example, when a door or a window is opened in warm weather, the temperature or amount of air blown from an air conditioner is controlled, such that the temperature in the cabin approaches a set temperature. In such a situation, it may be difficult to achieve a comfortable cooling condition by allowing the ports to continue to blow out temperature controlled air without adjustment. In such a situation, the cooling effect of most of the temperature controlled air may be wasted. Moreover, a heavy load may be applied to the compressor because of the refrigerant provided in the cooling circuit of the air conditioner, or to the blower because it is blowing conditioned air. Therefore, wasted power increases and the operation life of the equipment is reduced. Further, because the compressor usually is driven by utilizing the power of the vehicle engine, the load on the engine increases and overheating may occur.
Attempts to solve such problems include reducing the consumptive power of the air conditioner in response to the water temperature in the radiator, which is detected by a water temperature sensor, and reducing the consumptive power of an air conditioner by detecting when a door or a window is open by using a switch or a sensor on the door or the window.
Thus, under these methods, the consumptive power of an air conditioner may be appropriately reduced, and the overheating of a vehicle may be appropriately avoided, however, either a water temperature sensor, or a switch or a sensor for a door or a window may be needed. If such a sensor or a switch is not provided, it may be difficult to appropriately reduce the consumptive power of the air conditioner, or to appropriately avoid overheating. In particular, when a roof window or a double sliding window, which does not have a switch or a sensor, is opened, it may be difficult to appropriately reduce the consumptive power of the air conditioner or to appropriately avoid overheating.
Accordingly, it is an object of the present invention to provide an air conditioning system for vehicles, suitable for work vehicles, which may reduce waste power to prolong the life of the equipment, and which may achieve an improved and comfortable air conditioning state, even when a roof window or a double sliding window, with or without a switch, is open.
To achieve the foregoing and other objects, an air conditioning system for vehicles according to the present invention is provided. The air conditioning system for vehicles according to the present invention comprises a restriction control device for reducing the consumptive power of the air conditioning system by reducing a cooling ability of the air conditioner system when a cooling load for cooling an interior of the vehicle increases over a predetermined level and when predetermined conditions are satisfied.
In the air conditioning system of the present invention, the restriction control device may control certain ports to be opened or closed and control an amount of air discharged into the interior of the vehicle from the open ports, under a condition of reduced consumptive power. For example, the control device limits a port to be opened to only to a face mode port, under a condition of reduced consumptive power. Under such control, spot cooling an operator and reduction of the amount of air flow are each achieved. Therefore, an improved and comfortable air conditioning state depending on a present condition, an d an optimum operation condition with less waste power, may be both achieved.
The control device preferably returns the system from a condition of reduced cooling ability to a condition of normal cooling ability, when the cooling load decreases.
In particular, such an air conditioning system according to the present invention may be useful for a work vehicle.
In the air conditioning system according to the present invention, particularly in a work vehicle, even if a roof window or a double sliding window of a cabin is opened, ports to be opened are limited to those most suitable ports, depending on the conditions at the present time. Therefore, an improved and comfortable air conditioning state for an operator, and improved and optimum driving conditions with reduced waste power and reduced loads to the equipment, may be achieved. Comfortable spot cooling may be achieved particularly in the summer, because during the heat of the summer it is difficult to reduce the temperature of the cabin to a desired temperature when a roof window or a double sliding window is opened by allowing only a face mode port to be opened. Moreover, because the face mode port originally allows only a small amount of maximum air, the controlled air also may be reduced. Therefore, waste power may be reduced, the load applied to a blower or a compressor in a cooling circuit may be reduced, and the life of the equipment may be extended. Further, control may shift to another mode depending on the condition, by appropriately restricting the positions of the ports to be opened and the amount of air flow, while still maintaining comfortable air conditioning and improved driving conditions resulting in a reduction in waste power.
Further objects, features, and advantages of the present invention will be understood from the following detailed description of a preferred embodiment of the present invention with reference to the accompanying figures.